Dozens of Republican convention delegates are hatching a new plan to block Donald Trump at this summer’s party meetings, in what has become the most organized effort so far to stop the businessman from becoming the GOP presidential nominee. The moves come amid declining poll numbers for Trump and growing concern among Republicans that he is squandering his chance to defeat Democrat Hillary Clinton. Several controversies — including his racial attacks on a federal judge, his renewed call to temporarily ban Muslims from entering the United States and his support for changing the nation’s gun laws — have raised fears among Republicans that Trump is not really a conservative and is too reckless to run a successful race.